Transcript Using the model of a Punnett Square to predict offspring ratios

Using the model of a
Punnett Square to predict
offspring ratios
Objectives
► Objective
1: Students will know that chromosomes
have genes that control the phenotype
(appearance) of organisms
► Objective 2: Students will calculate the
percentages of various types of potential offspring
based on a simple dominance model and using a
single trait.
► Objective 3. Students will extend the model of the
Punnett Square in order to apply the concept of
simple dominance to new traits.
“Will your kids be able to
roll their tongues?”
Sperm + Egg = Offspring
►
We have been talking
about the idea of sperm
and egg getting together
to create a new life. We
know that this happens in
both plants and animals.
In animals, the male
contributes the sperm, and
the female contributes the
egg. In plants, the male
part of the plant
contributes pollen, which
acts like the sperm, and in
the female part of the
plant is the egg.
Mysteries & Inheritance
►
►
If we look at brothers or
sisters who all come from
the same parents, do
these brothers and sisters
all look exactly the same?
So are we not clones of
our parents?
What are some differences
between brothers or
sisters who come from the
same parents?
More questions
►
If you have a mother who is 5 feet 5 inches
tall and a father who is 6 feet tall, and they
have four children, how tall do you think
they should be? All the same?
►
Is it possible for a child to end up shorter
than both parents? Or taller than both
parents?
And what about…
► Have
any of you seen a person who looks
like they have the traits of one of their
grandparents but not the parent, like the
traits skipped a generation?
► Do any of you have traits more similar to
your grandmothers or grandfathers than
your parents?
To begin to understand how these kinds of
traits can be inherited, we have to go back
to the idea of the sperm and the egg
contributing to who we are.
23+23 46 Chromosomes
Female & Male
►These
paired chromosomes are made
up of thousands of sections called
genes. Each gene controls some kind
of trait, like color of hair, or color of
eyes, or contribute to height.
There are about 100,000 genes
that make up the human body.
Mother
Father
Free (F)
Attached (f)
Roll (R)
What is
interesting is that
we can tell a little
about what kind
of genes we have
by observing
various traits in
ourselves.
Not Roll (r)
Which form of the gene is dominant? Recessive?
Beaker Babies
FF
or
ff
Ff
?
Male
Punnett Square
f
F
F
e
m
a
l
e
F
f
FF
Ff
fF
ff
Phenotype Ratio (what shows): 3:1
Now to answer our question for
the day…
Male
r
F
e
m
a
l
e
r
r
rr
rr
r
rr
rr
Phenotype Ratio (what shows): 4:0
Tasks for the day:
1. If you can roll your tongue, what do you know about the
two genes that you have inherited? Explain.
► 2. If you cannot roll your tongue, what do you know about
the two genes you have inherited? Explain.
► 3. Using a Punnett Square, can you show if it is possible to
have another and a father who can roll their tongues, but
have children that cannot roll their tongues? Explain.
► 4. Using a Punnett Square, can you show if it is possible to
have a mother and a father who cannot roll their tongues,
but have children that can roll their tongues? Explain.
► 5. Extra challenge: Create a Punnett Square that
incorporates not one, but two traits (tongue rolling AND
earlobes). Hint: You will need a total of 16 cells in your
Punnett Square. Tell about the different kind of offspring
that are possible.
►
So what did we learn today?
► About
ourselves
► About
genes
► About
inheritance
► About
Punnett Squares
► About
science
Where are we going?
To study the particular diseases that
can be inherited & what those patterns
of inheritance are…
How did your partner help you
learn today?
What’s something you did well
together?
Say thanks & something you
appreciate about them.
Female- Body Cell Chromosomes
Male- Body Cell Chromosomes